Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$65.29	11.163%	$72.5783	$72.58	$72.60	$72.60
Purchase #2	$90.89	5.166%	$95.5854	$95.59	$95.60	$95.60
Purchase #3	$231.60	6.811%	$247.3743	$247.37	$247.35	$247.40
Purchase #4	$140.34	12.185%	$157.4404	$157.44	$157.45	$157.40
Purchase #5	$229.59	5.693%	$242.6606	$242.66	$242.65	$242.70
Purchase #6	$136.94	11.698%	$152.9592	$152.96	$152.95	$153.00
Purchase #7	$42.35	10.134%	$46.6417	$46.64	$46.65	$46.60
7 purchase totals =	$937.00		$1,015.2399	$1,015.24	$1,015.25	$1,015.30